Parasites and insects can negatively impact dairy cattle performance and profitability. My primary focus for this column is to share feeding strategies for fly control, but it is timely to mention two common parasites.
    Mange and lice are bothersome parasites that are present year-round and build during the cold weather months. They are most often found on cattle necks, backs, hips and tailhead areas. Controlling these parasites enhances productivity primarily by improving cow comfort and the behaviors associated with it. Treat all cattle on the property at the same time if possible, choosing a time when they are not stressed or in poor condition. If groups must be treated separately, they should be kept apart to ensure no contact between treated and untreated groups. Treatment programs often contain a general endectocide to cover both external parasites, such as mange and lice, and internal parasites. Consult your veterinarian or herd health professional for specific recommendations.
    Now back to flies. Fly control is critically important to all dairy operations to reduce the spread of disease and improve animal comfort, resulting in decreased stress and greater efficiency of growth or production.
    The largest economic return for fly control is effective cleanliness and sanitation. Flies reproduce in undisturbed damp organic matter. Removal and disposal of wasted feed, spilled milk or manure will go a long way in reducing fly populations. Residual premise spray is often beneficial throughout the summer to kill flies or deter other flies from coming into the dairy. Baiting or trapping flies is beneficial in certain locations. Parasitic wasps have also been used effectively to help control the pest fly population.  
    The key to any fly management strategy is to start early in the season before fly populations become a problem. As weather warms, we commonly add larvicides to calf and heifer feeds as well as any adult cows in housing situations that allow manure to accumulate over time. This generally starts in mid-April to early May in most of the Midwest. Larvicides will not get rid of current flies, but can go a long way in preventing future flies. Larvicides can also be sprayed on high-risk fly breeding areas, such as manure storage.
    How do larvicides administered in the feed work? These products pass through the animal, killing the fly larvae in the manure. Larvicides commonly used in dairy cattle include Rabon™, ClariFly® and Altosid®.
    Rabon™ is an organophosphate that has been used for years to control face flies, horn flies, house flies and stable flies. However, some resistance to this type of product can develop over time.
    ClariFly® contains diflubenzuron and is an insect growth regulator, and effectively controls house flies and stable flies common to confinement cattle. Female flies lay eggs in fresh manure. Eggs hatch into larvae that will feed and attempt to undergo three developmental stages. ClariFly® breaks the lifecycle by inhibiting the synthesis of the bug’s body wall, resulting in death before the larvae can become adult flies.
    Altosid® is used to a lesser extent to control horn flies more common in pasture cattle. Your nutritionist can assist with specific product recommendations.   
    Moderate to intense fly pressure can be stressful to dairy cattle in many ways and result in decreased profit. Flies are attracted to dairies due to the large amounts of feeding and breeding sites that exist on any operation. Cleanliness in these high-risk areas is a great place to start controlling flies, but this alone is not enough. Complementary fly control programs, such as spraying, baiting/trapping and larvicide feeding will go a long way to reducing fly populations and positively impacting productivity.
    Barry Visser is a nutritionist for Vita Plus.